this post from @coolcatteacher, Vicki Davis, referenced on Twitter. Even though "Spies Like Us" is three years old, it is still relevant and I'm sure there are many, many additional cases of teachers and students being called out by surreptitious video and audio recordings.
It is a reality of our modern life that video cameras are everywhere. Just do a YouTube search on your school. Even though many schools ban recording devices, you will most likely find video that has been uploaded.
I certainly don't have a solution to this problem, other than the advice to be mindful that you could be recorded at any time. One the one hand I find this thought to be an invasion of privacy, but on the other I wonder if this knowledge will help us become better teachers because we know that people could be watching. Even if it did make us better teachers, is this the right way to improve practice? We live in strange times, indeed.